Lead body with inner and outer co-axial coils

Abstract

A biomedical conductor assembly adapted for at least partial insertion in a living body. The conductor assembly includes a plurality of the first electrical conductors each covered with an insulator and helically wound in a first direction to form an inner coil with a lumen. A plurality of second electrical conductors each including a plurality of un-insulated wires twisted in a ropelike configuration around a central axis to form a plurality of cables. Each cable is covered with an insulator and helically wound in a second opposite direction forming an outer coil in direct physical contact with the inner coil. The inner and outer coils are covered by an insulator. A method of making the conductor assembly and implanting a neurostimulation system is also disclosed.

What is claimed is: 
     
       1. A biomedical conductor assembly adapted for at least partial insertion in a living body, the conductor assembly comprising:
 a plurality of first electrical conductors, each first electrical conductor being covered with a first insulator; 
 a plurality of second electrical conductors, each second electrical conductor being covered with a second insulator, wherein the plurality of the first electrical conductors are helically wound in a first direction to form an inner coil with a lumen, and the plurality of the second electrical conductors are helically wound in a second opposite direction to form an outer coil around an outside of the inner coil and in direct physical contact with the inner coil, wherein the inner coil is substantially concentric with the outer coil; and 
 an assembly insulator covering the inner and outer coils. 
 
     
     
       2. The conductor assembly of  claim 1 , wherein at least one of the plurality of first electrical conductors includes a plurality of un-insulated wires that are twisted in a ropelike configuration around a central axis to form a cable, wherein the cable is covered with the first insulator. 
     
     
       3. The conductor assembly of  claim 1 , wherein at least one of the plurality of second electrical conductors includes a plurality of un-insulated wires that are twisted in a ropelike configuration around a central axis to form a cable, wherein the cable is covered with the second insulator. 
     
     
       4. The conductor assembly of  claim 1 , wherein at least one of the plurality of second electrical conductors includes a plurality of un-insulated wires, the un- insulated wires being movable with respect to each other within the second insulator. 
     
     
       5. The conductor assembly of  claim 4 , wherein at least one of the un-insulated wires of the at least one of the plurality of second electrical conductors includes a core of a first material surrounded by a covering of a second material. 
     
     
       6. The conductor assembly of  claim 1 , wherein the inner coil is slidable relative to the outer coil within the conductor assembly. 
     
     
       7. The conductor assembly of  claim 1 , wherein at least one of the plurality of first electrical conductors includes a plurality of discrete insulated wires. 
     
     
       8. The conductor assembly of  claim 1 , wherein at least one of the plurality of second electrical conductors includes a center wire of a homogeneous material and a plurality of un-insulated wires that are twisted in a ropelike configuration around the center wire. 
     
     
       9. The conductor assembly of  claim 1 , wherein at least one of the plurality of second electrical conductors includes a plurality of un-insulated wires wrapped around a center wire, wherein the center wire includes a breaking strength greater than a breaking strength of the un-insulated wires. 
     
     
       10. A biomedical conductor assembly adapted for at least partial insertion in a living body, the conductor assembly comprising:
 a plurality of first electrical conductors that are each covered with a first insulator and are helically wound in a first direction to form an inner coil with a lumen; 
 a plurality of second electrical conductors that are helically wound in a second opposite direction forming an outer coil around an outside of the inner coil and in direct physical contact with the inner coil, wherein the inner coil is substantially concentric with the outer coil; and 
 an assembly insulator covering the inner and outer coils. 
 
     
     
       11. The conductor assembly of  claim 10 , wherein each of the first electrical conductors includes a plurality of un-insulated wires twisted in a ropelike configuration around a central axis. 
     
     
       12. The conductor assembly of  claim 10 , wherein each of the second electrical conductors includes a plurality of un-insulated wires twisted in a ropelike configuration around a central axis. 
     
     
       13. The conductor assembly of  claim 10 , wherein each of the second electrical conductors is covered with a second insulator. 
     
     
       14. The conductor assembly of  claim 10 , wherein at least one of the plurality of second electrical conductors includes a center wire of a homogeneous material and a plurality of un-insulated wires that are twisted in a ropelike configuration around the center wire. 
     
     
       15. The conductor assembly of  claim 10 , wherein at least one of the plurality of second electrical conductors includes a plurality of un-insulated wires wrapped around a center wire, wherein the center wire includes a breaking strength greater than a breaking strength of the un-insulated wires. 
     
     
       16. A therapy delivery element comprising:
 an elongated lead body including a proximal end and a distal end, the lead body including:
 a plurality of first electrical conductors, each of the plurality of first electrical conductors being covered with a first insulator and helically wound in a first direction to form an inner coil with a lumen; 
 a plurality of second electrical conductors, each of the plurality of second electrical conductors being covered with a second insulator and helically wound in a second opposite direction to form an outer coil around an outside of the inner coil and in direct physical contact with the inner coil, wherein the inner coil is substantially concentric with the outer coil; and 
 an assembly insulator covering the inner and outer coils. 
 
 
     
     
       17. The therapy delivery element of  claim 16 , wherein each of the first electrical conductors includes a plurality of un-insulated wires twisted in a ropelike configuration around a central axis. 
     
     
       18. The therapy delivery element of  claim 16 , wherein each of the second electrical conductors includes a plurality of un-insulated wires twisted in a ropelike configuration around a central axis. 
     
     
       19. The therapy delivery element of  claim 16 , wherein at least one of the plurality of second electrical conductors includes a center wire of a homogeneous material and a plurality of un-insulated wires that are twisted in a ropelike configuration around the center wire. 
     
     
       20. The therapy delivery element of  claim 16 , comprising a stylet wire including:
 a distal end configured to be inserted into the lumen of the inner coil through an opening at the proximal end of the lead body; and 
 a proximal end attached to a stylet handle.